2 Answers
2

At time of writing it still possible to run a GPU farm but at the speed of the increase in difficulty this will not last for long.

The second presumption with this is that you are not paying for the hardware, its very unlikely you would even break even if you had to purchase hardware at this time. The only real option in a competitive market is to go down the ASIC route.

Performance in a good quality ASIC can be 100 x that of a top end GPU. The price tag could realistically be about the same. There is zero comparison.

I wouldn't say that's totally true, I paid out for 2 second hand graphics cards (AMD 6950) and made even in a month or 2, admitantly I still had a motherboard, PSU and Case that was suited to work but breaking even is still easy enough, but yeah, I can see that the market is definitely hotting up, even in the last 2 months
– Peter FoxApr 10 '13 at 11:06

Not sure what you mean I said its still possible, just not for long :)
– MaxSanApr 10 '13 at 13:11

GPU best of breed can get you about 3.28MH/s/$ (excluding the cost of your PC)

FPGA best of breed can get you about 1.64MH/s/$

ASIC gets you about 50MH/s/$ - the value is likely lower now because Avalon (one of the ASIC provider) has increase their price by 4 times recently, and Butterfly Lab has not really started shipping their products

So to answer your question, yes, GPU can be a viable option if power cost is not a concern (including all the heat generated in the room).